J. Himalayan Ecol. Sustain. Dev. Vol.8 (2013) ISSN 0973-7502 SEDIMENT CHEMISTRY OF TSO KHAR, A HIGH ALTITUDE LAKE IN LADAKH Aftab Ahmad1*, Arshid Jehangir1, A.R. Yousuf1, 2, W.A. Shah3*, F.A Bhat4, Dilgeer Mehdi5 and A. Tanveer1 1Department of Environmental Science, University of Kashmir, Srinagar-190006 2 Expert Member, National Green Tribunal, New Delhi- 110001 3 Department of Chemistry, University of Kashmir, Srinagar, 190006 4Faculty of Fisheries, SKAUST-K, Shalimar, Srinagar 190006 5Govt. Degree College Nawa Kadal, University of Kashmir, Srinagar-190006 *Corresponding Authors email: [email protected]: [email protected] ABSTRACT Tso Khar is a shallow, saline land locked lake situated in eastern part of Ladakh, at an altitude of 4536 m (asl) and remains frozen for about three months during winter. There is no outlet to the lake and loss of water is through evapotranspiration and seepage. The lake sediments were found to be highly alkaline, especially in hypersaline zone (pH>10) with high conductivity (35000µS). Nitrate and exchangeable cations (Ca, Mg, Na and K) were significantly higher at hypersaline than fresh water zone, whereas organic carbon, organic matter, exchangeable phosphorus and total phosphorus were significantly higher at fresh water zone. Ammonia concentrations were high at saline sites but difference was insignificant. The progression of cation at saline site was Na> K> Mg>Ca whereas in fresh water expanse it was Ca> Mg> K>Na. The study revealed that the sediment chemistry of Tso Khar lake was mainly regulated by inflow components, selective removal of dissolved species and concentration processes in the lake basin. Keywords: Himalaya, hypersaline, endorheic, exchangeable cations, evapotranspiration, limnology INTRODUCTION about environmental changes occurring in both the water body and Lake sediments play an in the catchment area (Kalff, 2002; outstanding role in limnological Schmidt et al., 2002; de Vicente et studies as they can both reflect and al., 2006). Besides considering lake affect what is occurring in the sediments as a historical record, overlying water column (Håkanson, sediments may also affect the water 1984). In fact, sediments are the quality as a consequence of their product of lake life and, dynamic and active character consequently, they reflect the lake resulting from a great variety of type. In this sense, sediments can be biogeochemical reactions and regarded as a bank of information transformations (de Vicente et al., 1 J. Himalayan Ecol. Sustain. Dev. Vol.8 (2013) ISSN 0973-7502 2006). Sediments can function as Limited work has been either a source or a sink for many of carried out on Ladakh lakes the essential nutrients involved in the especially sediment chemistry eutrophication process (Ali et al., (Hutchison et al., 1943; Sekar, 1988). Exchange of nutrients 2000). The main constraints in this between sediments and overlying direction have been the extreme water column is regulated by climatic conditions, formidable topo- chemical characteristics of the water graphy and high altitude of the area. and of the sediments (Mortimer, In the present study, therefore, an 1971; Wetzel, 2001; Carling et al., attempt has been made to investigate 2013). Therefore sediment-water the sediment chemistry of the high- interactions are extremely important altitude lake Tso Khar. for understanding the whole nutrient dynamics in lakes (Boström et al., Study area and sites 1988). The biogeochemical environ- Tso Khar is a saline, land locked lake ment of sediments is generally located in the Ladakh region of anoxic and thus sites of reductive Jammu and Kashmir state between biogeochemical processes. The 32˚ 40' and 33˚15' N latitude and anaerobic sediments provide favour- 78˚15'and 78˚25' E longitude at an able conditions for generation and altitude of 4536 meters a.m.s.l. The lake is bounded by the Zanskar range accumulation of soluble sulfide H2S which are highly toxic to plants and in the south and Ladakh range in the are considered to be main cause of north. The basin is bounded by two disappearance and recession of longitudinal faults (Wünnemann et macrophytes (Holmer et al., 2005). al., 2010) and forms a graben The excessive organic matter in structure where the central block has sediments often contains high subsided to constitute a basin. The surface area of lake is 16.7 km2 with concentration of toxic organic acids, 2 and metabolic product which inhibit catchment area of about 1042 km . their growth (Mishra, 1938; Barko With strong seasonal fluctuations, and Simth, 1986; Brenda et al., the Tso Khar basin receives water 1993), thus playing key role in from nearby glaciers mainly in macrophytic distribution in lakes and spring and early summer via the wetlands. periodically active Pulong Kha Phu 2 J. Himalayan Ecol. Sustain. Dev. Vol.8 (2013) ISSN 0973-7502 river from the east and the perennial domestic livestock, mainly yaks and Nuruchan Lungpa river from the horses and pashmina goats for the south (Philip and Mazari, 2000). Champas. The marshes around the Both rivers enter the freshwater lake larger lake contain areas with Startsapuk Tso while the hyper- extensive deposits of natron, borax, saline Tso Khar is only fed by water and other salts. exchange through a small conduit between the two water expanses. There are a number of freshwater and hot springs within and around the periphery of the lake basin which act as water sources to the lake. Geologically the catchment of the Tso Khar comprises of Puga formation (Pre Cambrian), Sondu formation (cretaceous to Paleocene) and Liyan formation (Miocene). The Puga formation contains mainly micrictic limestone and gypsum. The region is characterized by extreme climatic conditions with local mean annual air temperature of about 4˚C, and annual precipitation less than 90 mm. Temperature during winter ranges from -20 to -40˚C (Bhattacharyya, 1989) while in summer it ranges from below 0˚C to 30˚C (Philip and Mazari, 2000). In the Tso Khar region vegetation cover comprises mainly desert steppe, scrub steppe and subnival cushion communities (Rawat and Adhikari, 2005). The basin popular is a popular seasonal grazing pasturing for 3 J. Himalayan Ecol. Sustain. Dev. Vol.8 (2013) ISSN 0973-7502 Fig. 1. Map of Tso Khar lake showing location of study sites Four sites were selected for the present study (Fig.1): Site TK1: The site was located in the northern part of the Tso Khar towards the eastern bank at 33º, 17.600' N and 78º, 03.156' E. The site was devoid of vegetation. The sediments were dark in colour with clayey texture. Site TK2: The site was located in the northern part near Thugji Gompa in the Tso Khar village towards the north eastern shore at 33º, 21.467' N and 78º, 01.400' E. The catchment area was covered by the green meadows. Site TK4: It was located in the northern part of the Tso Khar on western side at 33º, 19.450' N and 77º, 57.500' E. The site was devoid of vegetation. The sediments were brown in colour with clayey texture. Site TK5: It was located in the fresh water (southern) part of the Tso Khar in front of watching tower at 33º, 16.300' N and 78º, and 01.972' E. The site has a luxuriant growth of macrophytes. The sediments in this area were brown in colour with loamy texture. 4 J. Himalayan Ecol. Sustain. Dev. Vol.8 (2013) ISSN 0973-7502 MATERIAL AND METHODS extracted in 1N ammonium acetate solution by centrifugation Sediment samples were collected and decantation method in a 1:10 with the help of Ekman dredge soil extract ratio. Ca and Mg from the lake during 2004 to were estimated by versenate 2006 seasonal basis. The samples EDTA method, whereas Na and K were transported to laboratory in were estimated by digital flame deconta-minated polyethylene photometer (Systronics 130). bags. The analysis was carried out on wet as well dry samples. RESULTS AND DISCUSSION pH, conductivity, nitrate and ammonia were immedia-tely The mean sediment pH analyzed on wet samples whereas values were significantly higher the rest of parameters were (F3,32= 135.1; p = 0.000) at TK1 analyzed on air dry samples. pH (10.11±0.20) and TK4 (9.92±0.20) and conductivity was recorded by than at sites TK2 (8.27±0.31) and digital pH meter (Systronics- TK5 (8.30±0.40) (Fig.2a). The high MKVI) and digital conductivity pH (>8) in the sediments of Tso meter (Systronics-DB-104). Orga- Khar could be attributed to high nic carbon was estimated by precipitation rates of calcium and + Walkley and Black method,NH4 magnesium carbonates due to was measured using the indophenol alkalinity production via sulfate blue method (Page et al., 1982) reduction reactions from saline water NO3 was detrmined by Phenol- (Kilham and Cloke, 1990; Wang et disulfonic acid method (Jackson, al, 2007; Rodriguez et al., 2008). 1973). Available phosphorous Ryves et al. (2006) also reported that was measured by Olsen‘s method preferential precipitation of calcium and total phosphorus was carbonate with increase in salinity estimated spectrophotometrically leads to increase in pH. Conductivity (Model-Systronics 106) by molybd- is influenced by a variety of factors enum blue after triacid digestion like catchment geology, weathering method (Nitric acid: Sulphuric rate, and mineralization processes. acid: Perchloric acid in the ratio The conduc-tivity values of above of 9:4:1) (Page et al., 1982). 35000µS/cm were observed at saline Exchangeable cations were sites. The mean sediment 5 J. Himalayan Ecol. Sustain. Dev. Vol.8 (2013) ISSN 0973-7502 conductivity values were signifi- and the rate of microbial cantly (F3,32= 407.6; p = 0.000) decomposition (Godshalk and higher at TK1 and TK4 (Fig. 2b) Barko,1985; Bianchini et al., 2006; than TK2 and TK5.